Southwest Metropolitan Water and Sanitation District: Implementing a Phased Rehabilitation of an Entire Interceptor System

Abstract

The Southwest Metropolitan Water and Sanitation District (District) provides water distribution and sanitary sewer collection and transmission service to approximately 35,000 customers in the Denver Metropolitan area. The District’s sanitary sewer collection system includes approximately 18 miles of reinforced concrete pipe (RCP) interceptor sewers ranging in diameter from 15 inches through 60 inches. Most of the interceptors were constructed between 1963 and 1969. In 2011, the District identified several reaches of interceptor with severe deterioration due to hydrogen sulfide and sulfuric acid attack. The decision was made to rehabilitate the District’s interceptors with cured-in-place pipe (CIPP) methodology. The District developed a plan to rehabilitate all of their concrete interceptors over a period of five years. The D-Line and A-Line projects were designed and constructed in 2012 and 2013, respectively. Collectively, the two projects included installation of over 27,000 LF of CIPP ranging from 33-inches through 60-inches in diameter, rehabilitation of 95 manholes and vaults, and bypassing flows of up to 13.7 MGD. The D-Line was completed in 2012 for $2.3 million. The A-Line was completed in early 2014 for $3.5 million. The projects included work inside right-ofway of two state highways and required coordination with the Colorado Department of Transportation, U.S. Army Corps of Engineers, local parks and recreation departments, city and county officials, and several private residents and businesses. This paper discusses construction challenges encountered in the progress of the D-Line and A-Line projects including bypass installation, testing of manhole lining products, repairing a fiberglass flume damaged during CIPP installation, and failures of CIPP and manhole lining products. Construction of the C-Line project will be completed in summer of 2014. The C-Line will include rehabilitation of approximately 8,100 LF of 15-inch through 36inch sewer and 40 manholes. Two other phases are anticipated to follow the C-Line, 527 Pipelines 2014: From Underground to the Forefront of Innovation and Sustainability © ASCE 2014